Update to latest GNUstep core libraries.
Update dependent packages with more recent releases.
Remove old and bit-rotted ones.
Switch to using clang 3.3 and libobjc2 1.7 by default, so modern Objective-C
features work out of the box and remove a lot of configurable options for
sub-optimal (and, often, unsupported / deprecated upstream) configurations.
Take maintainership of GNUstep-related ports.
Several of the ports left in have scary warnings which mean that they are likely
broken in lots of cases. Future commits will fix them.
Approved by: bapt

Fix build when WITH_CCACHE_BUILD is set.
The problem is that WITH_CCACHE_BUILD adds PATH to the MAKE_ENV, but
the gnustep support sources a GNUStep.sh file that already sets the
PATH. Next when env PATH=... is called, it overwrites and losers the
gnustep PATH additions. This is a temporary fix until a better
solution is found.

- new options
USE_GNUSTEP_SYSTEM_APPS= ProjectCenter:devel/projectcenter.app
depends on Application installed in System directrory at runtime
USE_GNUSTEP_LOCAL_APPS= Ink:misc/gnustep-examples
depends on Application installed in Local directrory at runtime
USE_GNUSTEP_MAKE_DIRS= App Tools
call build and install target in each of the given dirs.